I have a card that is graded and attached to an order. I find the item in the list page, click edit, alter the Parallel, scroll down and click save. It then saves the card as a raw card and disassociates it from being graded. This happened to 4 cards testing different scenerios out. I'll have to figure out what they were so I'm glad it was only 4 that got messed up.
To get around this for now, just make sure when editing, to put the type back to graded before clicking save.